What’s Vulnerable › Vulnerabilities

CVE-2020-26967

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-12-09 · updated 2026-06-17

Description

When listening for page changes with a Mutation Observer, a malicious web page could confuse Firefox Screenshots into interacting with elements other than those that it injected into the page. This would lead to internal errors and unexpected behavior in the Screenshots code. This vulnerability affects Firefox < 83.

Affected products

• Mozilla Firefox: before 83.0 — fixed in 83.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 83.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1665820
• https://www.mozilla.org/security/advisories/mfsa2020-50/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1665820
• https://www.mozilla.org/security/advisories/mfsa2020-50/

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